1. Field of the Invention
This invention relates to surgery and orthopedic instrumentation. More particularly, this invention relates to a subtalar joint prosthesis and the surgical procedure and apparatus for its implantation.
2. Description of Prior Art
For many years there has been considerable interest and activity with respect to joint replacement in the foot and ankle, in which the degenerative articular surfaces of a joint are removed and replaced with an artificial joint, called a prosthesis, as a viable approach for the treatment of diseased or injured joints. Among the joints that can be considered for treatment in this manner is the subtalar joint, otherwise known as the talocalcaneal joint, which is comprised of the articulation between the talus and calcaneus bones. It is an essential joint of the foot, since it contributes to ankle stability, and the stress distribution and collaborative function of the hindfoot complex. Severe pain in this joint can also cause instability, limping and wear on other joints.
Fusion has long been a treatment for subtalar joint arthritis and disease. This approach has its drawbacks. It is known that limiting the motion in one joint will result in greater load distribution in adjacent joints, which can further degenerative disease. Other treatments include orthotics, braces, physical therapy and cortisone shots.
Many types of ankle joint prostheses have been developed over the past thirty years. Their use usually requires a surgeon to create, at the joint which is to be treated, a space which can accommodate the prosthesis. The size of the prosthesis will typically result in the resection of a significant amount of bone and the compromising of adjoining critical bony and soft tissue structures. This situation can lead to the diminishment over time of the stability of the orientation of such prosthesis and their ultimate failure.
Despite the development of many types of ankle joint prostheses, none has ever been developed for the subtalar joint. Thus, there is a need for the development of a subtalar joint prosthesis. There is also a need for the development of a surgical method to install such a prosthesis that will minimize the amount of bone loss associated with its implantation and therefore allowance for the preservation of the strongest portions of the distal talus and proximal calcaneus.